The connection state detecting device described in Patent Literature 1 is known as a device that measures alternating current (AC) power supplied to a load via a power line from a three-phase AC power source. The connection state detecting device makes a determination as follows to determine whether or not the connection of alligator clips (terminals) connected to a power line for measuring phase voltage, and the placement of a clamp sensor (current transformer) placed on the outer circumference of a power line for measuring phase current, are incorrect.
The connection state detecting device determines, from the phase voltage measured via the terminals, whether or not the effective value of the phase voltage is within a designated range, and whether or not the phase sequence is a predetermined sequence. In addition, the connection state detecting device determines, from the phase voltage measured via the terminals and the phase current measured via the current transformer, whether or not the phase difference between the phase voltage and the phase current for each phase is within a predetermined range, and whether or not the phase voltage or the phase current has no input.
The connection state detecting device determines that the terminal connection or the current transformer placement is incorrect in the case of any of when the effective value of the phase voltage is outside a designated range, when the phase sequence differs from a predetermined sequence, when the phase difference between the phase voltage and the phase current for each phase is outside a predetermined range, and when the phase voltage or the phase current has no input.